How can you warm up Mars?

Question

Mars experience extreme temperatures. Highest temperature being 21 degree celsius. So if we are to terraform mars one day then we first need to warm it up. So any ideas on how to warm up mars?

Answer 1

Mars is in a thermal equilibrium, where the same amount of energy as received is radiated away.

This leads to two broad categories of strategies.

1. Increase the amount of illumination. More energy in means the temperature of the system has to increase until a new equilibrium is reached. As we have no power source even close to the same power as the Sun, this means installing some kind of mirror in space to make more sun light hit Mars.

2. Decrease the heat loss. Less energy out means the means the temperature of the system has to increase until a new equilibrium is reached.
Proposed schemes include:

• Dark material covering the surface, reducing direct reflection
• Releasing natural volatiles into the atmosphere to block outbound thermal radiation ("greenhouse effect").
• Release artificial gasses with a much higher greenhouse potential.

These all run into the problem of being very large projects outside our current capability.

Answer 2

There's no consensus behind a simple solution. In a way, this is good news. We have multiple options, which needn't be mutually exclusive.

Mars has both dry ice and water ice (in the poles and to an unknown extent in the regolith), and each has a greenhouse effect. If Mars could be warmed enough to sublimate the former and melt and partially evaporate the latter, they would provide further radiative forcing. Proposals differ on how to initiate this.

Those focused on warming include importing other greenhouse gases, the in situ production of fluorine compounds with especially pronounced greenhouse effects, mirror-based increased insolation, albedo reduction with photosynthetic organisms, and the detonation of multiple nuclear bombs which has been critiqued for its cost, since mirrors continually heat while a bomb does so just once.

There are also aspects of terraforming with other motives noted to have a warming effect. For example, Mars has less water than Earth and negligible elemental oxygen, so we may wish to introduce water and rely on some of it photodissociating with appropriate catalysis. (This has also been proposed for Mercury, Venus and the Moon, and in practice what's delivered may be hydrogen to save on mass, as it can react with local oxides. This is especially applicable to Venus, where hydrogen can reduce the greenhouse effect.) Establishing an ecosystem would also require nitrogen, say from Titan. But the delivery of external matter converts GPE into heat, so the real issue is doing it slowly enough not to overheat the surface, which could cause such matter to escape Mars as a gas, unless it first has a (likely artificial) magnetosphere established.

Then there are aspects of terraforming which may inhibit warming Mars. For example, the consumption of carbon dioxide in photosynthesis to grow food thereby reduces the greenhouse effect. An ecosystem or civilization on Mars may have quite complex weathering effects on its rocks, and hence on how they change the fledgeling atmosphere.

Paraterraforming may use these ideas on a smaller scale, if only at first. Most Martian water ice is in its North pole. The North of the surface is at much lower altitude than the South, so existing water supplies would be confined to the lowlands without substantial infrastructure to distribute it. This likely includes water vapour, so there may be climate disparities during early terraforming.

Answer 3

The easiest way to warm Mars is by adding artificial greenhouse gases to the atmosphere. These would be manufactured in-situ. They could potentially trigger a runaway greenhouse effect, increasing CO2 in Mars atmosphere enough to increase surface temperature by about 50-60 K, and the pressure to about 30 kPa (300 mbar) or 30% of Earth's atmosphere. Colonists would no longer require astronaut suits but could just breath oxygen from portable tanks.

The "best combination" of CF4, C2F6, C3F8 and SF4 at a partial pressure of ∼0.2 Pa of or ∼0.4 Pa of C3F8 alone would increase the temperature of the planet enough to sublime CO2 reservoirs stored in the poles and absorbed in the surface regolith.

Such a combination alone would increase the temperature of Mars atmosphere by about 20 K. The outcome is potentially a runaway greenhouse effect.

I estimate about 6 billion tonnes of fluorine would need to be mined from Mars surface over, say, a 50 year period, requiring 250 million tonnes of fluorite (CaF2) to be mined per year. This is a relatively small mining operation compared to the total CO2 potentially released. (My calculation does not include sulphur for SF6.)

Depending on the amount of carbon available in a easily mobilisable state, the surface temperature could ultimately be increased by 60 K or more. Marinova et al have an estimate of a 50 K increase.

Many claim that Mars lack of a magnetosphere will immediately strip the atmosphere of the added greenhouse gases and CO2. This is a myth. Mars is well protected from solar wind. In fact the majority of gases lost from Mars are via Jeans Escape, which depends on upper atmosphere temperature and the planet's gravity. It also takes millions and possibly billions of years, giving plenty of time to "refill" the atmosphere.

Unfortunately, more recent research suggests there is NOT ENOUGH CO2 in the Martian poles and absorbed in regolith to produce a runaway greenhouse effect. The easily mobilisable CO2 on Mars may increase the atmospheric pressure of CO2 to only 7% of Earth's atmosphere (about 7 kPa, 70 mbar)

Note that there is plenty of CO2 in carbonate rocks, but this requires high temperature processing to release, with impractically large energy supplies.

An increase of 20 K without the runaway greenhouse would still be an improvement, but without adding large amounts of CO2, it's far short of what's needed for full terraforming and humans on Mars working without pressure suits.

While many other ways of heating Mars are suggested, these require operations with huge energy requirements, space-based technologies that we can only imagine, and at a scale far beyond manufacturing fluorocarbons on Mars using technologies currently used on Earth.